Combining micro-computed tomography with histology to analyze biomedical implants for peripheral nerve repair.

BACKGROUND: Biomedical implants used in tissue engineering repairs, such as scaffolds to repair peripheral nerves, can be too large to examine completely with histological analyses. Micro-computed tomography (micro-CT) with contrast agents allows ex vivo visualization of entire biomaterial implants and their interactions with tissues, but contrast agents can interfere with histological analyses of the tissues or cause shrinkage or loss of antigenicity. NEW METHOD: Soft tissue, ex vivo micro-CT imaging using Lugol's iodine was compatible with histology after using a rapid (48 h) method of removing iodine. RESULTS: Adult normal and repaired rat sciatic nerves were infiltrated ex vivo with iodine, imaged with micro-CT and then the iodine was removed by incubating tissues in sodium thiosulfate. Subsequent paraffin sections of normal nerve tissues showed no differences in staining with hematoxylin and eosin or immunostaining with multiple antibodies. Iodine treatment and removal did not alter axonal diameter, nuclear size or relative area covered by immunostained axons (p>0.05). Combining imaging modalities allowed comparisons of macroscopic and microscopic features of nerve tissues regenerating through simple nerve conduits or nerve conduits containing a titanium wire for guidance. COMPARISON WITH EXISTING METHODS: Quantification showed that treatment with iodine and sodium thiosulfate did not result in tissue shrinkage or loss of antigenicity. CONCLUSIONS: Because this combination of treatments is rapid and does not alter tissue morphology, this expands the ex vivo methods available to examine the success of biomaterial implants used for tissue engineering repairs.